// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2008-2009 Patrick McHardy <kaber@trash.net>
 * Copyright (c) 2012 Pablo Neira Ayuso <pablo@netfilter.org>
 * Copyright (c) 2012 Intel Corporation
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/string.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_tables.h>
#include <net/ip.h>

struct nft_nat {
        u8                      sreg_addr_min;
        u8                      sreg_addr_max;
        u8                      sreg_proto_min;
        u8                      sreg_proto_max;
        enum nf_nat_manip_type  type:8;
        u8                      family;
        u16                     flags;
};

static void nft_nat_setup_addr(struct nf_nat_range2 *range,
                               const struct nft_regs *regs,
                               const struct nft_nat *priv)
{
        switch (priv->family) {
        case AF_INET:
                range->min_addr.ip = (__force __be32)
                                regs->data[priv->sreg_addr_min];
                range->max_addr.ip = (__force __be32)
                                regs->data[priv->sreg_addr_max];
                break;
        case AF_INET6:
                memcpy(range->min_addr.ip6, &regs->data[priv->sreg_addr_min],
                       sizeof(range->min_addr.ip6));
                memcpy(range->max_addr.ip6, &regs->data[priv->sreg_addr_max],
                       sizeof(range->max_addr.ip6));
                break;
        }
}

static void nft_nat_setup_proto(struct nf_nat_range2 *range,
                                const struct nft_regs *regs,
                                const struct nft_nat *priv)
{
        range->min_proto.all = (__force __be16)
                nft_reg_load16(&regs->data[priv->sreg_proto_min]);
        range->max_proto.all = (__force __be16)
                nft_reg_load16(&regs->data[priv->sreg_proto_max]);
}

static void nft_nat_setup_netmap(struct nf_nat_range2 *range,
                                 const struct nft_pktinfo *pkt,
                                 const struct nft_nat *priv)
{
        struct sk_buff *skb = pkt->skb;
        union nf_inet_addr new_addr;
        __be32 netmask;
        int i, len = 0;

        switch (priv->type) {
        case NFT_NAT_SNAT:
                if (nft_pf(pkt) == NFPROTO_IPV4) {
                        new_addr.ip = ip_hdr(skb)->saddr;
                        len = sizeof(struct in_addr);
                } else {
                        new_addr.in6 = ipv6_hdr(skb)->saddr;
                        len = sizeof(struct in6_addr);
                }
                break;
        case NFT_NAT_DNAT:
                if (nft_pf(pkt) == NFPROTO_IPV4) {
                        new_addr.ip = ip_hdr(skb)->daddr;
                        len = sizeof(struct in_addr);
                } else {
                        new_addr.in6 = ipv6_hdr(skb)->daddr;
                        len = sizeof(struct in6_addr);
                }
                break;
        }

        for (i = 0; i < len / sizeof(__be32); i++) {
                netmask = ~(range->min_addr.ip6[i] ^ range->max_addr.ip6[i]);
                new_addr.ip6[i] &= ~netmask;
                new_addr.ip6[i] |= range->min_addr.ip6[i] & netmask;
        }

        range->min_addr = new_addr;
        range->max_addr = new_addr;
}

static void nft_nat_eval(const struct nft_expr *expr,
                         struct nft_regs *regs,
                         const struct nft_pktinfo *pkt)
{
        const struct nft_nat *priv = nft_expr_priv(expr);
        enum ip_conntrack_info ctinfo;
        struct nf_conn *ct = nf_ct_get(pkt->skb, &ctinfo);
        struct nf_nat_range2 range;

        memset(&range, 0, sizeof(range));

        if (priv->sreg_addr_min) {
                nft_nat_setup_addr(&range, regs, priv);
                if (priv->flags & NF_NAT_RANGE_NETMAP)
                        nft_nat_setup_netmap(&range, pkt, priv);
        }

        if (priv->sreg_proto_min)
                nft_nat_setup_proto(&range, regs, priv);

        range.flags = priv->flags;

        regs->verdict.code = nf_nat_setup_info(ct, &range, priv->type);
}

static const struct nla_policy nft_nat_policy[NFTA_NAT_MAX + 1] = {
        [NFTA_NAT_TYPE]          = { .type = NLA_U32 },
        [NFTA_NAT_FAMILY]        = { .type = NLA_U32 },
        [NFTA_NAT_REG_ADDR_MIN]  = { .type = NLA_U32 },
        [NFTA_NAT_REG_ADDR_MAX]  = { .type = NLA_U32 },
        [NFTA_NAT_REG_PROTO_MIN] = { .type = NLA_U32 },
        [NFTA_NAT_REG_PROTO_MAX] = { .type = NLA_U32 },
        [NFTA_NAT_FLAGS]         =
                NLA_POLICY_MASK(NLA_BE32, NF_NAT_RANGE_MASK),
};

static int nft_nat_validate(const struct nft_ctx *ctx,
                            const struct nft_expr *expr)
{
        struct nft_nat *priv = nft_expr_priv(expr);
        int err;

        if (ctx->family != NFPROTO_IPV4 &&
            ctx->family != NFPROTO_IPV6 &&
            ctx->family != NFPROTO_INET)
                return -EOPNOTSUPP;

        err = nft_chain_validate_dependency(ctx->chain, NFT_CHAIN_T_NAT);
        if (err < 0)
                return err;

        switch (priv->type) {
        case NFT_NAT_SNAT:
                err = nft_chain_validate_hooks(ctx->chain,
                                               (1 << NF_INET_POST_ROUTING) |
                                               (1 << NF_INET_LOCAL_IN));
                break;
        case NFT_NAT_DNAT:
                err = nft_chain_validate_hooks(ctx->chain,
                                               (1 << NF_INET_PRE_ROUTING) |
                                               (1 << NF_INET_LOCAL_OUT));
                break;
        }

        return err;
}

static int nft_nat_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
                        const struct nlattr * const tb[])
{
        struct nft_nat *priv = nft_expr_priv(expr);
        unsigned int alen, plen;
        u32 family;
        int err;

        if (tb[NFTA_NAT_TYPE] == NULL ||
            (tb[NFTA_NAT_REG_ADDR_MIN] == NULL &&
             tb[NFTA_NAT_REG_PROTO_MIN] == NULL))
                return -EINVAL;

        switch (ntohl(nla_get_be32(tb[NFTA_NAT_TYPE]))) {
        case NFT_NAT_SNAT:
                priv->type = NF_NAT_MANIP_SRC;
                break;
        case NFT_NAT_DNAT:
                priv->type = NF_NAT_MANIP_DST;
                break;
        default:
                return -EOPNOTSUPP;
        }

        if (tb[NFTA_NAT_FAMILY] == NULL)
                return -EINVAL;

        family = ntohl(nla_get_be32(tb[NFTA_NAT_FAMILY]));
        if (ctx->family != NFPROTO_INET && ctx->family != family)
                return -EOPNOTSUPP;

        switch (family) {
        case NFPROTO_IPV4:
                alen = sizeof_field(struct nf_nat_range, min_addr.ip);
                break;
        case NFPROTO_IPV6:
                alen = sizeof_field(struct nf_nat_range, min_addr.ip6);
                break;
        default:
                if (tb[NFTA_NAT_REG_ADDR_MIN])
                        return -EAFNOSUPPORT;
                break;
        }
        priv->family = family;

        if (tb[NFTA_NAT_REG_ADDR_MIN]) {
                err = nft_parse_register_load(ctx, tb[NFTA_NAT_REG_ADDR_MIN],
                                              &priv->sreg_addr_min, alen);
                if (err < 0)
                        return err;

                if (tb[NFTA_NAT_REG_ADDR_MAX]) {
                        err = nft_parse_register_load(ctx, tb[NFTA_NAT_REG_ADDR_MAX],
                                                      &priv->sreg_addr_max,
                                                      alen);
                        if (err < 0)
                                return err;
                } else {
                        priv->sreg_addr_max = priv->sreg_addr_min;
                }

                priv->flags |= NF_NAT_RANGE_MAP_IPS;
        }

        plen = sizeof_field(struct nf_nat_range, min_proto.all);
        if (tb[NFTA_NAT_REG_PROTO_MIN]) {
                err = nft_parse_register_load(ctx, tb[NFTA_NAT_REG_PROTO_MIN],
                                              &priv->sreg_proto_min, plen);
                if (err < 0)
                        return err;

                if (tb[NFTA_NAT_REG_PROTO_MAX]) {
                        err = nft_parse_register_load(ctx, tb[NFTA_NAT_REG_PROTO_MAX],
                                                      &priv->sreg_proto_max,
                                                      plen);
                        if (err < 0)
                                return err;
                } else {
                        priv->sreg_proto_max = priv->sreg_proto_min;
                }

                priv->flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
        }

        if (tb[NFTA_NAT_FLAGS])
                priv->flags |= ntohl(nla_get_be32(tb[NFTA_NAT_FLAGS]));

        return nf_ct_netns_get(ctx->net, family);
}

static int nft_nat_dump(struct sk_buff *skb,
                        const struct nft_expr *expr, bool reset)
{
        const struct nft_nat *priv = nft_expr_priv(expr);

        switch (priv->type) {
        case NF_NAT_MANIP_SRC:
                if (nla_put_be32(skb, NFTA_NAT_TYPE, htonl(NFT_NAT_SNAT)))
                        goto nla_put_failure;
                break;
        case NF_NAT_MANIP_DST:
                if (nla_put_be32(skb, NFTA_NAT_TYPE, htonl(NFT_NAT_DNAT)))
                        goto nla_put_failure;
                break;
        }

        if (nla_put_be32(skb, NFTA_NAT_FAMILY, htonl(priv->family)))
                goto nla_put_failure;

        if (priv->sreg_addr_min) {
                if (nft_dump_register(skb, NFTA_NAT_REG_ADDR_MIN,
                                      priv->sreg_addr_min) ||
                    nft_dump_register(skb, NFTA_NAT_REG_ADDR_MAX,
                                      priv->sreg_addr_max))
                        goto nla_put_failure;
        }

        if (priv->sreg_proto_min) {
                if (nft_dump_register(skb, NFTA_NAT_REG_PROTO_MIN,
                                      priv->sreg_proto_min) ||
                    nft_dump_register(skb, NFTA_NAT_REG_PROTO_MAX,
                                      priv->sreg_proto_max))
                        goto nla_put_failure;
        }

        if (priv->flags != 0) {
                if (nla_put_be32(skb, NFTA_NAT_FLAGS, htonl(priv->flags)))
                        goto nla_put_failure;
        }

        return 0;

nla_put_failure:
        return -1;
}

static void
nft_nat_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
{
        const struct nft_nat *priv = nft_expr_priv(expr);

        nf_ct_netns_put(ctx->net, priv->family);
}

static struct nft_expr_type nft_nat_type;
static const struct nft_expr_ops nft_nat_ops = {
        .type           = &nft_nat_type,
        .size           = NFT_EXPR_SIZE(sizeof(struct nft_nat)),
        .eval           = nft_nat_eval,
        .init           = nft_nat_init,
        .destroy        = nft_nat_destroy,
        .dump           = nft_nat_dump,
        .validate       = nft_nat_validate,
        .reduce         = NFT_REDUCE_READONLY,
};

static struct nft_expr_type nft_nat_type __read_mostly = {
        .name           = "nat",
        .ops            = &nft_nat_ops,
        .policy         = nft_nat_policy,
        .maxattr        = NFTA_NAT_MAX,
        .owner          = THIS_MODULE,
};

#ifdef CONFIG_NF_TABLES_INET
static void nft_nat_inet_eval(const struct nft_expr *expr,
                              struct nft_regs *regs,
                              const struct nft_pktinfo *pkt)
{
        const struct nft_nat *priv = nft_expr_priv(expr);

        if (priv->family == nft_pf(pkt) ||
            priv->family == NFPROTO_INET)
                nft_nat_eval(expr, regs, pkt);
}

static const struct nft_expr_ops nft_nat_inet_ops = {
        .type           = &nft_nat_type,
        .size           = NFT_EXPR_SIZE(sizeof(struct nft_nat)),
        .eval           = nft_nat_inet_eval,
        .init           = nft_nat_init,
        .destroy        = nft_nat_destroy,
        .dump           = nft_nat_dump,
        .validate       = nft_nat_validate,
        .reduce         = NFT_REDUCE_READONLY,
};

static struct nft_expr_type nft_inet_nat_type __read_mostly = {
        .name           = "nat",
        .family         = NFPROTO_INET,
        .ops            = &nft_nat_inet_ops,
        .policy         = nft_nat_policy,
        .maxattr        = NFTA_NAT_MAX,
        .owner          = THIS_MODULE,
};

static int nft_nat_inet_module_init(void)
{
        return nft_register_expr(&nft_inet_nat_type);
}

static void nft_nat_inet_module_exit(void)
{
        nft_unregister_expr(&nft_inet_nat_type);
}
#else
static int nft_nat_inet_module_init(void) { return 0; }
static void nft_nat_inet_module_exit(void) { }
#endif

static int __init nft_nat_module_init(void)
{
        int ret = nft_nat_inet_module_init();

        if (ret)
                return ret;

        ret = nft_register_expr(&nft_nat_type);
        if (ret)
                nft_nat_inet_module_exit();

        return ret;
}

static void __exit nft_nat_module_exit(void)
{
        nft_nat_inet_module_exit();
        nft_unregister_expr(&nft_nat_type);
}

module_init(nft_nat_module_init);
module_exit(nft_nat_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>");
MODULE_ALIAS_NFT_EXPR("nat");
MODULE_DESCRIPTION("Network Address Translation support");